Stabilized multivibrator



y 1951 c. H. HOEPPNER 2,560,576

STABILIZED MULTIVIBRATOR Filed April 16. 1946 5 Sheets-Sheet l ma i l'JRIGGER PULSE y 1951 c. H. HOEPPNER 2,560,576

STABILIZED MULTIVIBRATOR Filed April 16, 1946 y 5 Sheets-Sheet 2awe/whoa CONRAD H. HOE PPNER July 17, 1951 c. H. HOEPPNER 2,560,575

STABILIZED MULTIVIBRATOR Filed April 16, 1945 5 Sheets-Sheet 5 IIITRIGGER PUL'SE IN VEN TOR.

CONRAD H. HOEPPNER Attmznley 5 Sheets-Sheet 4 C. H. HOEPPNER STABILIZEDMULTIVIBRATOR mwuam mww j July 17, 1951 Filed April 16, 1946 Elma/whoa Pfl H M R E N P P E O H H D A R N o C July 17, 1951 c. H. HOEPPN'ER2,560,576

I STABILIZED MULTIVIBRATOR Filed April 16, 1946 5 Sheets-Sheet 5 LISzJQINVENTOR. CONRAD H. HOEPPNER Afton/my Patented July 17, 1951 UNITEDSTATES ATENT OFFICE (Granted under the act of March 3, 1883, as amendedApril 30, 1928; 370 0. G. 757) 6 Claims.

This invention relates to improvements in regenerative types ofelectronic trigger circuits.

The type of electronic trigger circuit to which the invention relatescomprises in general a pair of vacuum tubes the control electrodes ofwhich are so cross-connected to the anodes of the other tubes as toproduce one stable state wherein one of the tubes is held normallyconducting and the other non-conducting. This state remains or persistsuntil a signal from an external source is impressed upon the circuitwhereupon the con-. ducting conditions of the tubes are reversed and inwhich condition the circuit will remain for a time depending upon thetime constants incorporated in the circuit. An alternate arrangementexists where the tubes are so interconnected that the conductingconditions of the two tubes automatically reverse or oscillate back andforth, that arrangement depending upon the time-constant incorporated inthe circuit.

The present invention is designed to improve the control of the timeduration of one of these states of the regenerative type of triggercircuit by the use of an inductor-capacitor network, located so that itis sensitive to changes in voltages thereupon and acts upon thecontrolling electrodes of the regenerative type of electronic triggercircuit.

An object of this invention is to provide a control for accuratelytiming the duration of one of the states in a regenerative type triggercircuit.

Another obiect of the invention is to provide a control which canaccurately limit the time duration of one of the states in aregenerative type of trigger circuit to any desired value less than thevalue depending on the time-constants of the circuit.

Fig. 1 is a detailed circuit diagram of one exem lary embodiment of mvinvention.

Fig. 2 shows representative voltage plots pertaining to the circuitdiagram of Fig. 1.

Fig. 3 is a detailed circuit dia ram of another exemplary embodiment ofmy invention.

Fig. 4 shows representative voltage plots pertaining to the circuitdiagram of Fig. 3.

Fig. 5 is a detailed circuit diagram of still another exemplaryembodiment of my invention.

Fig. 6 shows representative voltage plots pertaining to the circuitdiagram of Fig. 5.

Fig. 7 is a detailed circuit diagram of another exemplary embodiment ofmy invention.

Fig. 8 shows representative voltage plots pertaining to the circuitdiagram of Fig. '7.

Fig. 9 is a detailed circuit diagram of another exemplary embodiment ofmy invention.

' state.

Fig. 10 shows representative voltage plots pertaining to the circuitdiagram of Fig. 9.

The operation of an electronic trigger circuit constructed in accordancewith the teachings of the invention can be better understood uponreference to Fig. 1, where one typical embodiment of the invention isillustrated. As herein exemplified the circuit comprises a pair ofvacuum tubes 9 and I0, arranged so as to sustain one stable statewherein tube 9 is conducting and tube H1 is non-conducting. The activestate is when tube 9 is cut-off and tube 10 is conducting. During theactive state output pulses may be obtained from the plates of tube 9 andtube l 6. These output pulses will be essentially square, the one fromthe plate of tube 9 being positive and the one from the plate of tubeI!) being negative. In considering the stable state of the circuit it isapparent that, as long as no voltage from an external source is beingapplied to it, the grid of tube 9 will be conducting and will have apotential very slightly above the cathode potential. This is due to thefact that the grid is connected through inductor H and resistors l2 and25 to 3+ while the cathode is at ground potential. The voltage On theplate of tube 9 is therefore low because of the voltage drop across theresistor l3. The grid of tube It, being connected between the plate oftube 9 and C- is held below cut-off by means of resistors l4 and I5.Hence the voltage on the plate of tube [0 is B-land the voltage acrosscapacitor I6 is almost 13+.

If a negative pulse of sufiicient value is now applied to the grid oftube 9 the tube can be cutoff. The plate potential will start to risealmost immediately and very rapidly. This rise in potential will betransmitted to the grid of tube Ill through capacitor I! and will causetube in to start to conduct. Hence the plate potential of tube II] willlower because of the voltage drop across the resistor l8 and, throughcapacitor is will lower the grid potential of tube 9 even more. Thus itcan be seen that a regenerative action occurs to drive the triggercircuit to the active Owing to the potential on the plate of tube Illand the charge on the capacitor is the grid of tube 9 will be held belowcut-off. It will, however, gradually rise as the capacitor It dischargesthrough resistors l2 and I8 and inductor l I.

During this active state, i. e., while the grid of tube 9 is belowcut-off, the potential on the plate of tube 9 will remain high andthereby provide the positive output pulse as shown in wave-.

3 form D of Fig. 2. The potential on the plate of tube III will remainlow and provide the negative output pulse as shown in waveform E of Fi2.

When the grid potential of tube 9 reaches cutoff the tube will againstart to conduct thereby lowering the plate potential. The grid of tubeID, being connected to the plate of tube 9 through capacitor I! willlikewise drop thus reducing the current through tube In and therebyraising the plate voltage. This raise is coupled back to the grid oftube 9 by capacitor Hi to raise it and produce a regenerative actionwhich rapidly drives the trigger circuit back to the stable state.

An observation of Fig. 1 will disclose that an inductor-capacitorringing circuit has been..incorporated between resistor l2 and capacitorI6. The effect of this circuit will be to'modify the grid potentialsexponential rise as capacitor l6 attempts to discharge and then chargewith reversed polarity. As was seen, the grid of. tube 9 was conductingcurrent before the negative trigger pulse was applied to it. Abruptly itbecame non-conducting and tube it] started to conduct. This reversal ofconditions causes a surge of discharge current through capacitor 16which also passes through the inductor capacitor circuit. The.inductor-capacitor circuit' is, thereby, shocked into voltageoscillation, shown in waveform B of Fig. 2 as the voltage at point Uwith respect to point T. These oscillations are superimposed in theexponential dischargecharge' curve of capacitor l5 thus causing .thegrid signal of tube 9 to appear as shown in waveform C ofFig'. 2, wheredotted line CO represents the cut-off potential of tube 9.

A further examination of waveform C of Fig. 2 will reveal how' myinvention acts to limit the time duration of the pulse. The normal,gradual rise of the grid to cut-off is shown'by. the dashed line Q. Withmy invention the rise to cut-off is much more abrupt and therefore moreaccurate. Furthermore, by choosing the proper values for inductor I Iand capacitor 19 the. amplitude of the oscillations can be varied. Hencethe cut-ofi potential can be reached on any desired one Of severaloscillations. This, of course, provides an accurate and stable controlonthe time duration of the output pulse.

Upon the return of tube 9 to the conducting state the oscillatorycomponent of the grid signal is swinging positive. The accompanyingchange in capacitor l6 from a discharging to a charging state causes areduction of current through inductor I! which, in turn, kicks theoscillations in the inductor-capacitor network in an additive direction.Unless a tubewithextremely low grid impedance is used, one-half cyclelater, the oscillations will drive the grid below cut-ofi so that thetrigger circuit will be free running, stabilized in both directions bythe resonant circuit. To obviate this repeating phenomena resistor 25 isinserted between the grid of tube 9 and a point between capacitor 16 andthe inductor capacitor network. This resistor is selected so that thesteady state voltage at point U will be above the peak value oftheoscillatory voltage.

In the second embodiment of the invention, which is shown in Fig. 3, twoinductor capacitor ringing circuits, 2D and 2|, arranged in series, areused instead of one circuit as in Fig. 1. The operation of the triggercircuit is the same as described before but the voltage oscillations atpoint W with respect to point V are'cyclic m .4 amplitude as shown bywaveform G of Fig. 4. This is accomplished by tuning 20 and 2| todifferent frequencies to establish a beat frequency having the desiredhalf period. With this cyclic oscillatory voltage superimposed on thenormal grid otential rise Q the actual grid voltage of tube" 9 is asshown in waveform H of Fig. 4. By the use of voltage oscillations whichare cyclic in amplitude any danger there might be of the grid potentialreaching cut-off on the wrong oscillation may be obviated.

In Fig. 5 the inductor-capacitor network is in the form of ashort-circuited artificial transmission line 22. The action of thetrigger circuit is the same as described before. In this case, however;the ability of the line to reflect the original trigger signal is used.By using a short circuited line the trigger pulse is reflected with thereverse polarity as shown in waveform J of Fig. 6. This reflected pulseis superimposed on the voltage curve of the grid of tube 9 as showndotted in waveform K of Fig. 6. This method results in a very accuratecontrol of the time of the pulse duration. It is necessary however, inthis method, to use a triggering pulse of such an amplitude that theamplitude of the pulse when reflected will be suflicient to raise thegrid voltage to cutoff. Since it takes 2N /LC (where N is the number ofsections in the delay line, L is the individual value of the inductorsand C is the individual value of the capacitors used), seconds for thetriggering pulse to travel down the delay line and be reflected backthis will be the time duration of the output pulse.

In Fig. 7 an artificial transmission line 22 is again employed. One endis shorted and the other or sending end is terminated in an impedancewhich is greater than the characteristic impedance of the line. Thisline will oscillate in square'waves when a voltage is impressed acrossthe sending end. Waveform L in Fig. 8 shows a negative pulse from a highimpedance source which is impressed on the grid of tube 9. As tube 9cuts off and tube It] commences to conduct a portion of the voltage dropin resistor I8 is coupled to the grid of tube 9 through capacitor l6 andis also impressed across the artificial transmission line 22. Waveform Mshows the voltage oscillations appearing across the sending end of thetransmission line. Waveform N shows the signal on the grid of tube 9which is waveform M superimposed on the exponential discharge curve Q ofcapacitor iii. As shown by the waveforms the; grid is raised rapidly tocut-off potential by a wavefront which has traveled down the line andback three complete times. The pulse put out by this circuit can beterminated by anyone of the positive excursions of the wavefront whichappears across the sending end of the line. These positive excursionsoccur at times Y 2N /LC, where Y'is any odd number and 2N /LC is'thetime required for a wavefront to travel down the transmission line andback as explained in'the previous example.

Fig. 9 is an embodiment of my invention in a regenerative type triggercircuit in which the conducting conditions of the two tubesautomatically reverse. To understand this circuit assume first that tube9 is conducting and that tube I9 is non-conducting owing to a charge oncapacitor l1. Since tube 9 is conducting a direct current will beflowing through inductor H. Capacitor I! will discharge throughresistor23 and tube 9, however, until the grid potential of tube l0 reaches Cll-Off. At this point tube 10 will begin gas-ca to conduct and, becauseof the potential drop acrossresistor IS, the voltage on the anode oftube ID will decrease. A portion of this decrease Will be transmitteddirectly to the grid of tube 3 through capacitor it so that tube 9 willbe cutoif. By the same type of regenerative action described in detailbefore, the grid potential of tube 9 will be driven considerably belowcut-01f and will then tend to rise gradually as capacitor l6 dischargesthrough-resistor 24 and tube I In the meantime, however, the cessationof our-- rent-flow through tube 9 will have resulted in current andvoltage oscillations in the inductorcapacitor network H and I9, shown inwaveform O of Fig. 10 as the cathode signal taken with respect toground. The production of such oscillations has likewise been describedpreviously in the discussion of Fig. 1. (More than oneinductor-capacitor ringing circuit can be used, as before.) Due to theseoscillations the relative approach of the grid voltage to the cathodevoltage will not be merely gradual but will be modifled to be alsooscillatory as shown in waveform P of Fig. 10. This waveform is theexponential discharge curve of capacitor l6 minus waveform 0.

Hence the net result will be identical with the condition whichprevailed in the discussion of Fig. 1, i. e., the voltage differencebetween the grid and the cathode voltages will suddenly, on one of theoscillations, become less than the difference needed to maintain thetube non-conducting. The tube will begin to conduct and theaforementioned type of regenerative action will cause the triggercircuit to revert to the condition first assumed.

Although I have shown and described only limited and specificembodiments of the present invention it is to be understood that I amfully aware of the many modifications possible thereof. Therefore thisinvention is not to be restricted except insofar as is necessitated bythe spirit of the prior art and the scope of the appended claims.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

What is claimed is:

l. A circuit of the regenerative electronic trigger type comprising atleast two vacuum tubes each of which has an anode, a grid, and acathode, an impedance connection from the grid of each tube to the anodeof the other tube operative to form an electronic trigger circuit inwhich only one vacuum tube will conduct at a time, an inductor-capacitornetwork incorporated in the grid circuit of one of said tubes operativeresponsive to the establishment of non-conduction in said one of saidtubes to produce non-self-sustaining voltage oscillations, saidconnections including means operative in response to an input triggeringimpulse to temporarily produce an unstable state wherein said one tubeis held nonconducting and the other conducting for the duration ofseveral of said voltage oscillations, said oscillations being eifectiveto stabilize the time interval said one of said tubes remainsnonconducting.

2. A circuit of the regenerative electronic trigger type comprising atleast two vacuum tubes each of which has an anode, a grid, and acathode, an impedance connection from the grid of each tube to the anodeof the other tube operative to form an electronic trigger circuit inwhich only one vacuum tube will conduct at a time, two or moreinductor-capacitor circuits serially connected together and incorporatedin the grid circuit of one of said tubes operative responsive to theestablishment of non-conduction in said one of said tubes to producenon-self-sustaining voltage oscillations, said connections includingmeans operative in response to an input triggering impulse totemporarily produce an unstable state wherein said one tube is heldnon-conducting and the other conducting for the duration of several ofsaid voltage oscillations, said oscillations being effective tostabilize the time interval said one of said tubes remainsnonconducting.

3. A circuit of the regenerative electronicjtrig ger type comprising atleast two vacuum tubes each of which has an anode, a grid, and acathode, an impedance connection from the grid of each tube to the anodeof the other tube operative to form an electronic trigger circuit inwhich only one vacuum tube will conduct at a time, a short circuitedartificial transmission line incorporated in the grid circuit of one ofsaid tubes operative responsive to the establishment of non-conductionin said one of said tubes to produce non-selfsustaining voltageoscillations, said connections including means operative in response toan input triggering impulse to temporaril produce an unstable statewherein said one tube is held nonconducting and the other conducting forthe duration of several of said voltage oscillations, said oscillationsbeing eifective to stabilize the time interval said one of said tubesremains non-conducting.

4. A circuit of the regenerative electronic trigger type comprisin atleast two vacuum tubes each of which has an anode, a grid, and acathode, an impedance connection from the grid of each tube to the anodeof the other tube operative to form an electronic trigger circuit inwhich only one vacuum tube will conduct at a time, an inductor-capacitornetwork incorporated in the grid circuit of one of said tubes operativeresponsive to the establishment of non-conduction in said one of saidtubes to produce non-self-sustaining voltage oscillations, saidconnections including means operative to produce in said trigger circuita stable state wherein one of said tubes is held conducting and theother non-conducting and further operative in response to an inputtriggering impulse to temporarily produce an unstable state wherein saidone tube is held non-conducting and the other conductin for the dtuationof several of said voltage oscillations, said oscillations beingeffective to stabilize the time interval said one of said tubes remainsnon-conducting.

5. A circuit of the regenerative electronic trigger type comprising atleast two vacuum tubes each of which has an anode, a grid, and acathode, an impedance connection from the grid of each tube to the anodeof the other tube operative to form an electronic trigger circuit inwhich only one vacuum tube will conduct at a time, two or moreinductor-capacitor circuits serially connected together and incorporatedin the grid circuit of one of said tubes operative responsive to theestablishment of non-conduction in said one of said tubes to producenon-self-sustaining voltage oscillations, said connections includingmeans operative in response to an input triggering impulse totemporarily produce an unstable state wherein said one tube is heldnon-conducting and the other conducting for the duration of everal ofsaid voltage oscillations, said oscillations being said tubes remainsnon-conducting.

6. A circuit of the regenerative electronic trigger type comprising atleast two vacuum tubes each of which has an anode, a grid, and acathode, an impedance connection from the grid of each tube to the anodeof the other tube operative to form an electronic trigger circuit. inwhich only one vacuum tube will conduct at a time, a short circuitedartificial transmission line incorporated in the grid circuit of one ofsaid tubes operative responsive to the establishment of non-conductionin said one of said tubes to produce non-selfsustaining voltageoscillations, said connections including means operative in response toan input triggering impulse to temporarily produce an unstable statewherein said one tube is held nonconducting and the other conducting forthe duration of several of said voltage oscillations, said oscillationsbeing effective to stabilize the time interval said one of said tubesremains non-conducting.

CONRAD H. HOEPPNER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,419,772 Gottier Apr. 29, 19472,426,996 Goodall Sept. 9, 1947 2,436,808 Jacobsen et a1. Mar. 2, 19482,442,770 Kenyon June 8, 1948 2,445,448 Miller July 20, 1948

